A PRESS SECTION APPARATUS

Abstract: A press section apparatus (10) is disclosed for pressing water from a formed web (W). The apparatus (10) includes a first extended nip press (N1) for pressing a first portion of water from the web (W). A press felt (12) extends through the first press (N1), and a suction turning roll (14) is disposed downstream relative to the first press (N1) for guiding the press felt (12) and for urging the web (W) towards and around the turning roll (14). A second extended nip press (N2) is disposed downstream relative to the turning roll (14). The second press (N2) includes a backing roll (16) having a smooth circumferential surface (18) such that the web (W) follows the surface (18) when the web (W) emerges from the second press (N2). A transfer arrangement (20) transfers the web (W) away from the smooth surface (18) and onto a further press felt (22) which is disposed downstream relative to the smooth surface (18). A third extended nip press (N3) is disposed downstream relative to the transfer means (20) for controlling two-sidedness of the resultant web (W).

Description: A PRESS SECTION APPARATUS Background Of The Invention Field Of The Invention The present invention relates to a press section apparatus for pressing water from a formed web. More specifically, the present invention relates to an extended nip press. Information Disclosure Statement U.S. Patent No. 4,257,844 to Schmitt et al teaches a double felted vented nip press followed by a suction turning roll with a vented roll couple press disposed immediately downstream relative to the turning roll. Furthermore, U.S. Patent No. 4,988,410 to Albrecht teaches an ENP, the bearing blanket and felt of which transport the pressed web past a further extended nip press shoe for removing further water from the web. However, in the arrangement taught by the '410 patent, the web is unstable after the first extended nip at the point of separation of the respective press felts. Accordingly, there is a tendency for high pressure air or steam within the first ENP to blow the web away from the press felt 1 1 . Additionally, with the '410 arrangement, the web tends to be thrown off of the felt by centrifugal force as the web travels around the FLEX-O-NIP type roll upstream relative to the second extended nip press. The present invention overcomes the aforementioned advantage by the provision of a second extended nip press disposed downstream relative to the first extended nip press but with a suction turning roll interposed therebetween so that the web is stabilized prior to and after the web reaches the suction turning roll. Therefore it is a primary objective of the present invention to overcome the aforementioned disadvantages of the prior art arrangements and to provide a press section apparatus which makes a considerable contribution to the art of pressing a formed web. Summary Of The Invention The present invention relates to a press section apparatus for pressing water from a formed web. The apparatus includes first extended nip press for pressing a first portion of water from the web. A press felt extends through the first extended nip press and a suction turning roll is disposed downstream relative to the first extended nip press for guiding the press felt and for urging the web towards and around the turning roll. A second extended nip press is disposed downstream relative to the turning roll. The second press includes a backing roll having a smooth circumferential surface such that the web follows the surface when the web emerges from the second extended nip press. A transfer means transfers the web away from the smooth surface onto a further press felt which is disposed downstream relative to the smooth surface. The arrangement is such that the transfer means transfers the web from the smooth surface onto the further press felt. Also, a third extended nip press is disposed downstream relative to the transfer means for controlling two-sidedness of the resultant web. In a more specific embodiment of the present invention, the first extended nip press includes a first extended nip press shoe and a second press felt which is disposed between the first extended nip press shoe and the web. A first vented controlled deflection roll cooperates with the first shoe. The arrangement is such that the web is disposed between the press felt and the second press felt. During movement of the press felt, the web and the second press felt are disposed between the first vented deflection roll and the first extended nip press shoe. The first extended nip press further includes a vented extended nip press blanket which is disposed between the first extended nip press shoe and the second press felt. In one embodiment of the present invention, the first extended nip press shoe is a hydrodynamic shoe, and in another embodiment of the present invention, the first press shoe is a hydrostatic shoe. The suction turning roll is connected to a source of partial vacuum such that the web is urged towards the press felt when the press felt and the second press felt diverge relative to each other. The second extended nip press includes a second extended nip press shoe which is disposed within a loop defined by the press felt. The press section apparatus also includes a second vented blanket which is disposed between the second extended nip press shoe and the press felt. The second extended nip press shoe, according to one embodiment of the present invention, is a hydrodynamic shoe, and in another embodiment of the present invention, is a hydrostatic shoe. The second extended nip press includes a second controlled deflection backing roll which cooperates with the second extended nip press shoe for removing a second portion of water from the web. The transfer means includes a lead-in roll which is disposed in close proximity to the smooth surface and downstream relative to the second press shoe for leading the pressed web from the smooth surface towards the further press felt. Additionally, the transfer means includes a suction transfer roll which is disposed within a further loop defined by the further press felt such that the web supported by the further press felt is guided from the lead-in roll towards the third extended nip press. The third extended nip press includes a third extended nip press shoe which is disposed within the further loop. Additionally, the third extended nip press includes a third vented blanket which is disposed between the third press shoe and the further press felt. In one embodiment of the present invention, the third press shoe is a hydrodynamic shoe, and in another embodiment of the present invention, the third press shoe is a hydrostatic shoe. The third extended nip press also includes a third controlled deflection controlled backing roll which cooperates with the third extended nip press shoe for pressing the web and for controlling two-sidedness of the resultant web. Many modifications and variations of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter, taken in conjunction with the annexed drawings. However, such modifications and variations fall within the spirit and scope of the present invention as defined by the appended claims. Brief Description Of The Drawings Figure 1 is a side-elevational view of the press section apparatus according to the present invention; and Figure 2 is a similar view to that shown in Figure 1 , but shows the respective extended nip presses having hydrostatic rather than hydrodynamic shoes. Similar reference characters refer to similar parts throughout the various views of the drawings. Detailed Description Of The Drawings Figure 1 is a side-elevational view of a press section apparatus, generally designated 10 according to the present invention, for pressing water from a formed web W. The apparatus 10 includes a first extended nip press N1 for pressing a first portion of water from the web W. A press felt 12 extends through the first extended nip press N1 , and a suction turning roll 14 is disposed downstream relative to the first extended nip press Nl for guiding the press felt 12 and for urging the web W towards and around the turning roll 14. A second extended nip press N2 is disposed downstream relative to the turning roll 14. The second extended nip press N2 includes a backing roll 16 having a smooth circumferential surface 18 such that the web W follows the surface 18 when the web W emerges from the second extended nip press N2. Transfer means, generally designated 20, transfer the web W away from the smooth surface 18 to a further press felt 22 which is disposed downstream relative to the smooth surface 18. The arrangement is such that the transfer means 20 transfers the web W from the smooth surface 18 onto the further press felt 22. A third extended nip press N3 is disposed downstream relative to the transfer means 20 for controlling two-sidedness of the resultant web W. The first extended nip press N1 includes a first extended nip press shoe 24. The press N1 also includes a second press felt 26 which is disposed between the first extended n ? press shoe 24 and the web W. A first vented controlled deflection roll 28 cooperates with the first shoe 24, the arrangement being such that the web W is disposed between the press felt 12 and the second press felt 26 during movement of the press felt 12, the web W and the second press felt 26 between the first vented deflection roll 28 and the first extended nip press shoe 24. The first extended nip press N1 also includes a vented extended nip press blanket 30 which is disposed between the first extended nip press shoe 24 and the second press felt 26. As shown in Figure 1 , the first extended nip press shoe 24 is a hydrodynamic shoe. However, in an alternative embodiment of the present invention as shown in Figure 2, the first extended nip press shoe 24A is a hydrostatic shoe. The suction turning roll 14 is connected to a source of partial vacuum 32 such that the web W is urged towards the press felt 12 when the press felt 12 and the second press felt 26 diverge relative to each other. The second extended nip press N2 includes a second extended nip press shoe 34 which is disposed within a loop defined by the press felt 12. The press section apparatus 10 also includes a second vented blanket 36 which is disposed between the second extended nip press shoe 34 and the press felt 12. In one embodiment of the present invention, the second extended nip press shoe is a hydrodynamic shoe, as indicated in Figure 1 , and in a second embodiment of the present invention as shown in Figure 2, the second extended nip press shoe 34A is a hydrostatic shoe. The second extended nip press N2 includes the backing roll 16 which is a second controlled deflection backing roll. The backing roll 16 cooperates with the second extended nip press shoe 34 for removing a second portion of water from the web W. The transfer means 20 includes a lead-in roll 38 which is disposed in close proximity to the smooth surface 18 and downstream relative to the second press shoe 34 for leading the pressed web W from the smooth surface 18 towards the further press felt 22. The transfer means 20 also includes a suction transfer roll 40 which is disposed within a further loop defined by the further press felt 22. The arrangement is such that the web W supported by the further press felt 22 is guided from the lead-in roll 38 towards the third extended nip press N3. The third extended nip press N3 includes a third extended nip press shoe 42 disposed within the further loop. The third extended nip press shoe 42 cooperates with a third vented blanket 44 which is disposed between the third press shoe 42 and the further press felt 22. In the embodiment shown in Figure 1 , the third press shoe 42 is a hydrodynamic shoe, whereas in Figure 2, the third press shoe 42A is a hydrostatic shoe. The third extended nip press N3 also includes a third controlled deflection controlled backing roll 46 which cooperates with the third extended nip press shoe 42 for pressing the web W and for controlling two-sidedness of the resultant web. Figure 2 shows an alternative embodiment of the present invention in which each of the press shoes 24A,34A and 42A is a hydrostatic shoe, rather than a hydrodynamic shoe. In other respects, the arrangement shown in Figure 2 is identical to that shown in Figure 1 , and similar reference characters are used to identify similar parts, such numerals having the suffix "A" added thereto. In operation of the press section apparatus according to the present invention, the web is fully supported through the first extended nip press N1A between cooperating felts 12A and 26A. Subsequently, the suction turning roll 14 guides the web supported by the felt 12 so that the web W is guided through the second nip N2. The arrangement particularly enables stabilization of the relatively wet web from the first extended nip press N1 to the second extended nip press N2. The web adheres to the smooth surface 18 of the backing roll 16 and is doctored therefrom so that a tail can be threaded under the lead roll 38 and drawn onto the further felt 22 for guidance through the third nip press N3. The present invention provides a significant improvement over the prior art presses and avoids the problem of blowing the unstable pressed web away from a supporting press felt when such web emerges from a first extended nip press.

Claims: What is Claimed is: 1 . A press section apparatus (10) for pressing water from a formed web (W), said apparatus comprising: a first extended nip press (N1 ) for pressing a first portion of water from the web (W); a press felt (12) extending through said first extended nip press (N1 ); a suction turning roll (14) disposed downstream relative to said first extended nip press (N1 ) for guiding said press felt (12) and for urging the web (W) towards and around said turning roll (14); a second extended nip press (N2) disposed downstream relative to said turning roll (14); said second extended nip press (N2) including: a backing roll (16) having a smooth circumferential surface (18) such that the web (W) follows said surface (18) when the web (W) emerges from said second extended nip press (N2); transfer means (20) for transferring the web (W) away from said smooth surface (18); a further press felt (22) disposed downstream relative to said smooth surface (18), the arrangement being such that said transfer means (20) transfers the web (W) from said smooth surface (18) onto said further press felt (22); and a third extended nip press (N3) disposed downstream relative to said transfer means (20) for controlling two-sidedness of the resultant web (W). 2. A press section apparatus as set forth in claim 1 , wherein said first extended nip press (N1 ) includes: a first extended nip press shoe (24); a second press felt (26) disposed between said first extended nip press shoe (24) and the web (W); a first vented controlled deflection roll (28) cooperating with said first shoe (24), the arrangement being such that the web (W) is disposed between said press felt (12) and said second press felt (26) during movement of said press felt (12), the web (W) and said second press felt (26) between said first vented deflection roll (28) and said first extended nip press shoe (24). 3. A press section apparatus as set forth in claim 2, wherein said first extended nip press (N1 ) further includes: a vented extended nip press blanket (30) disposed between said first extended nip press shoe (24) and said second press felt (26). 4. A press section apparatus as set forth in claim 2, wherein said first extended nip press shoe (24) is a hydrodynamic shoe. 5. A press section apparatus as set forth in claim 2, wherein said first extended nip press shoe (24A) is a hydrostatic shoe. 6. A press section apparatus as set forth in claim 2, wherein said suction turning roll (14) is connected to a source of partial vacuum (32) such that the web (W) is urged towards said press felt (12) when said press felt (12) and said second press felt (26) diverge relative to each other. 7. A press section apparatus as set forth in claim 1 , wherein said second extended nip press (N2) includes: a second extended nip press shoe (34) disposed within a loop defined by said press felt (12). 8. A press section apparatus as set forth in claim 7, further including: a second vented blanket (36) disposed between said second extended nip press shoe (34) and said press felt (12). 9. A press section apparatus as set forth in claim 7, wherein said second extended nip press shoe (34) is a hydrodynamic shoe. 10. A press section apparatus as set forth in claim 7, wherein said second extended nip press shoe (34A) is a hydrostatic shoe. 1 1. A press section apparatus as set forth in claim 7, wherein said second extended nip press (N2) includes: a second controlled deflection backing roll which cooperates with said second extended nip press shoe (34) for removing a second portion of water from the web (W). 12. A press section apparatus as set forth in claim 1 , wherein said transfer means (20) includes: a lead-in roll (38) disposed in close proximity to said smooth surface (18) and downstream relative to said second press shoe (34) for leading the pressed web (W) from said smooth surface (18) towards said further press felt (22); a suctior transfer roll (40) disposed within a further loop defined by suid further press felt (22) such that the web (W) supported by said further press felt (22) is guided from said lead-in roll (38) towards said third extended nip press (N3). 1 3. A press section apparatus as set forth in claim 1 2, wherein said third extended nip press (N3) includes: a third extended nip press shoe (42) disposed within said further loop. 14. A press section apparatus as set forth in claim 1 3, wherein said third extended nip press (N3) includes: a third vented blanket (44) disposed between said third press shoe (42) and said further press felt (22). 1 5. A press section apparatus as set forth in claim 1 3, wherein said third press shoe (42) is a hydrodynamic shoe. 1 6. A press section apparatus as set forth in claim 13, wherein said third press shoe (42A) is a hydrostatic shoe. 1 7. A press section apparatus as set forth in claim 13, wherein said third extended nip press (N3) further includes: a third controlled deflection backing roll (46) which cooperates with said third extended nip press shoe (42) for pressing the web (W) and for controlling two-sidedness of the resultant web.

Inventors: SCHMITT ARNOLD JOSEPH, SCHMITT, ARNOLD, JOSEPH
Applicants: BELOIT TECHNOLOGIES INC, BELOIT TECHNOLOGIES, INC.
Application year: 1994
Main classification: D21F3
IPC codes: D21F3